View source for HD 97950

{{Short description|Multiple star system in the constellation Carina}}
{{Infobox open cluster|
| name = [[Henry Draper Catalogue|HD]] 97950
| image = [[File:NGC 3603b.jpg|280px]]
|caption=[[Hubble Space Telescope|HST]] image of the HD 97950 cluster
| epoch = [[J2000]]
| class =
| constellation = [[Carina (constellation)|Carina]]
| ra = {{RA|11|15|07.346}}<ref name=ucac/>
| dec = {{Dec|-61|15|38.52}}<ref name=ucac/>
| dist_ly = 25 kly
| dist_pc = 7.6 kpc<ref name=melena2008>{{cite journal|bibcode=2008AJ....135..878M|title=The Massive Star Content of NGC 3603|journal=The Astronomical Journal|volume=135|issue=3|pages=878–891|last1=Melena|first1=Nicholas W.|last2=Massey|first2=Philip|last3=Morrell|first3=Nidia I.|last4=Zangari|first4=Amanda M.|year=2008|doi=10.1088/0004-6256/135/3/878|arxiv = 0712.2621 |s2cid=16765414}}</ref>
| appmag_v = 9.03<ref name=ducati>{{cite journal|bibcode=2002yCat.2237....0D|title=VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system|journal=CDS/ADC Collection of Electronic Catalogues|volume=2237|pages=0|last1=Ducati|first1=J. R.|year=2002}}</ref>
| size_v =
| mass_kg =
| mass_msol = 19,000<ref name=pang2013>{{cite journal|bibcode=2013ApJ...764...73P|title=On the Origin of Mass Segregation in NGC 3603|journal=The Astrophysical Journal|volume=764|issue=1|pages=73|last1=Pang|first1=Xiaoying|last2=Grebel|first2=Eva K.|last3=Allison|first3=Richard J.|last4=Goodwin|first4=Simon P.|last5=Altmann|first5=Martin|last6=Harbeck|first6=Daniel|last7=Moffat|first7=Anthony F. J.|last8=Drissen|first8=Laurent|year=2013|doi=10.1088/0004-637X/764/1/73|arxiv = 1212.4566 |s2cid=119199840}}</ref>
| radius_ly = 120"<ref name=pang2013/>
| v_hb =
| age =
| notes = Main cluster in [[NGC 3603]]
| names=[[Henry Draper Catalogue|HD]]&nbsp;97950, [[NGC 3603]]YC, [[Durchmusterung|CD]]-60°3452, [[Durchmusterung|CPD]]-60° 2732, [[Hipparcos catalogue|HIP]]&nbsp;54948, [[Wolf-Rayet star|MR]]&nbsp;38, [[Wolf-Rayet star|WR]]&nbsp;43
}}

'''HD 97950''', is the central core of a [[super star cluster]] within the [[NGC 3603]] [[H II region]] (similar to [[R136]] within the [[Tarantula Nebula]]).  It was catalogued as a single star, but has now been resolved into one of the densest clusterings of stars in the galaxy.

Only the six lettered stars A-F at the core of the cluster are typically referred to as components of HD 97950, while the remaining stars of the cluster and surrounding area are usually numbered as members of NGC 3603.  The cluster itself is still called the HD 97950 cluster as well as the NGC 3603 young cluster (NGC 3603YC).  There are no other notable groupings of stars in NGC 3603 and the HD 97950 cluster is often loosely referred to as simply NGC 3603.

==Members==
[[File:NGC3603 core.jpg|thumb|left|upright=1.0|The core of the cluster, with A1/2/3 at the very centre, and B and C to its left]]
The main components are designated [[NGC 3603-A1|A1]], A2, A3, [[NGC 3603-B|B]], and [[NGC 3603-C|C]], of which A1 and C are known to be spectroscopic binaries.  A1a, A1b, and C are all WN6h [[Wolf–Rayet star]]s, amongst the [[list of most massive stars|most massive]] and [[list of most luminous stars|luminous known]].<ref name=crowther/>

There are several dozen early O class stars (O3 and O4) in the cluster, mostly main sequence stars.  There are just a handful of giants and supergiants including:  one prominent early B supergiant, [[Sher 25]]; a highly luminous O3.5 supergiant, [[Sher 18]]; and an interesting carbon-rich O9.7 supergiant, [[Sher 23]].

Over 7,500 stars have been identified in the cluster, with the least massive being smaller than the sun and the most massive over {{solar mass|100}}.  Stars less than about {{solar mass|4}} have not yet reached the main sequence.<ref name="harayama2008">{{cite journal|last1=Harayama|first1=Y.|last2=Eisenhauer|first2=F.|last3=Martins|first3=F.|year=2008|title=The Initial Mass Function of the Massive Star-forming Region NGC 3603 from Near-Infrared Adaptive Optics Observations|journal=The Astrophysical Journal|volume=675|issue=2|pages=1319–1342|arxiv=0710.2882|bibcode=2008ApJ...675.1319H|doi=10.1086/524650|s2cid=17905999}}</ref>

Generally, only the stars with letter naming are typically referred to as components of HD 97950, more stars are listed in [[NGC 3603]].

{{-}}
{| class="wikitable sortable"
|-
!BLW name
!MDS number
!Other names
!Spectral type
!m<sub>V</sub>
!M<sub>V</sub>
!Temperature
([[Kelvin|K]])
!Luminosity
('''{{solar luminosity|link=y}}''')
!Reference
|-
|[[NGC 3603-A1|A1]]
|30
|WR 43a (HSW 1)
|WN6h/WN6h
|11.18
| -7.8
|42,000/40,000
|2,455,000/1,514,000
|<ref name="crowther" /><ref name="moffat1994">{{cite journal|last1=Moffat|first1=Anthony F. J.|last2=Drissen|first2=Laurent|last3=Shara|first3=Michael M.|year=1994|title=NGC 3603 and its Wolf-Rayet stars: Galactic clone of R136 at the core of 30 Doradus, but without the massive surrounding cluster halo|journal=Astrophysical Journal|volume=436|pages=183|bibcode=1994ApJ...436..183M|doi=10.1086/174891|doi-access=free}}</ref><ref name="harayama2008" />
|-
|A2
|31
|HSW 4
|O3V
|12.53
| -6.9
|46,500
|1,500,000
|<ref name="moffat1994" /><ref name="harayama2008" />
|-
|A3
|26
|HSW 5
|O3III
|13.09
| -6.4
|46,500
|863,000
|<ref name="moffat1994" /><ref name="harayama2008" />
|-
|[[NGC 3603-B|B]]
|23
|WR 43b (HSW 2)
|WN6h
|11.33
| -7.9
|42,000
|2,884,000
|<ref name="crowther" /><ref name="harayama2008" />
|-
|[[NGC 3603-C|C]]
|18
|WR 43c (HSW 3)
|WN6h
|11.89
| -7.3
|44,000
|2,239,000
|<ref name="crowther" /><ref name="harayama2008" />
|-
|D1
|49
|
|O4V
|12.64
| -6.3
|44,000
|
|<ref name="massey2005">{{cite journal|last1=Massey|first1=Philip|last2=Puls|first2=Joachim|last3=Pauldrach|first3=A. W. A.|last4=Bresolin|first4=Fabio|last5=Kudritzki|first5=Rolf P.|last6=Simon|first6=Theodore|year=2005|title=The Physical Properties and Effective Temperature Scale of O-Type Stars as a Function of Metallicity. II. Analysis of 20 More Magellanic Cloud Stars and Results from the Complete Sample|journal=The Astrophysical Journal|volume=627|issue=1|pages=477–519|arxiv=astro-ph/0503464|bibcode=2005ApJ...627..477M|doi=10.1086/430417|s2cid=18172086}}</ref><ref name="moffat1994" /><ref name="harayama2008" />
|-
|D2
|50
|
|O5V
|12.74
| -6.2
|41,000
|
|<ref name="massey2005" /><ref name="moffat1994" /><ref name="harayama2008" />
|-
|D3
|52
|
|O4V
|13.68
| -5.2
|44,000
|
|<ref name="massey2005" /><ref name="moffat1994" /><ref name="harayama2008" />
|-
|E
|19
|MMM 104
|O5.5III(f)
|12.83
| -6.1
|41,000
|1,038,000
|<ref name="melena2008" /><ref name="massey2005" /><ref name="moffat1994" />
|-
|F
|39
|MTT 6
|O5V
|11.86
| -6.1
|41,000
|
|<ref name="massey2005" /><ref name="moffat1994" /><ref name="harayama2008" />
|-
|G
|61
|MTT 10
|O5V
|12.74
| -6
|41,000
|
|<ref name="massey2005" /><ref name="moffat1994" /><ref name="harayama2008" />
|}

The number of WNh and early O stars exceeds any known cluster in the galaxy. The [[Quintuplet Cluster|Quintuplet]] and [[Arches Cluster|Arches]] clusters each have around 20 young massive stars and may have masses comparable to the HD 97950 cluster, but they contain no O3 or WN6 stars at all. The rich red supergiant clusters such as [[Westerlund 1]] are too old to contain such stars, although may be even more massive. [[R136]] in the [[Large Magellanic Cloud]] contains stars more massive than any in HD 97950, as well as large numbers of early O stars, and the cluster as a whole may be ten times as massive.<ref name=zwart>{{cite journal|bibcode=2010ARA&A..48..431P|title=Young Massive Star Clusters|journal=Annual Review of Astronomy and Astrophysics|volume=48|pages=431–493|last1=Portegies Zwart|first1=Simon F.|last2=McMillan|first2=Stephen L. W.|last3=Gieles|first3=Mark|year=2010|doi=10.1146/annurev-astro-081309-130834|arxiv = 1002.1961 |s2cid=119207843}}</ref>

It has been proposed that the star [[WR 42e]], found 2.6 [[arcmin]] from the centre of the cluster, and [[J1117−6120]], an O6V runaway a quarter of a degree away on the other side of the cluster, were both ejected in a 3-body interaction.  Two of the stars then merged to form the extremely massive and luminous WR 42e.<ref name=3body>{{cite journal |title= Two massive stars possibly ejected from NGC 3603 via a three-body encounter |journal= Monthly Notices of the Royal Astronomical Society: Letters|last1=Gvaramadze  |first1=V. V.|last2=Kniazev  |first2=A. V.|last3=Chené |first3=A. -N.|last4=Schnurr |first4=O. |volume= 430|pages= L20–L24|date= 2012|doi=10.1093/mnrasl/sls041 |doi-access= free|bibcode=2013MNRAS.430L..20G|arxiv = 1211.5926 |s2cid= 56103308}}</ref>

==Mass==
The HD 97950 cluster has a total photometric mass of {{solar mass|10,000–16,000}},<ref name=harayama2008/> and a dynamical mass of {{solar mass|19,000}}.<ref name=pang2013/>  The constituent stars have apparently dynamical segregated with the more massive stars predominantly found at the centre of the cluster.<ref name=pang2013/>  The centre of the cluster has a density of {{solar mass|60,000}} pc<sup>−3</sup>, ten times the [[Orion Nebula]] and comparable to R136.<ref name=harayama2008/>

==Age==
Fitting the main sequence, and pre-main sequence gives a cluster age of 1 million years or less.  There is no clear [[main sequence turnoff]], although the most massive stars are modelled best with an age of 2.5 million years, but are compatible with an age around one million years.<ref name=harayama2008/>  A small number of stars, for example Sher 25, apparently show much greater ages and it has been suggested that there is either ongoing star formation, or an earlier burst of star formation.<ref name=melena2008/>  Other studies have estimated ages up to 2 million years, but the existence of the most massive and luminous stars provide a hard upper limit of 2.5 million years on the possible age.<ref>{{cite journal|bibcode=2012ApJ...750L..44K|title=Instantaneous Starburst of the Massive Clusters Westerlund 1 and NGC 3603 YC|journal=The Astrophysical Journal Letters|volume=750|issue=2|pages=L44|last1=Kudryavtseva|first1=Natalia|last2=Brandner|first2=Wolfgang|last3=Gennaro|first3=Mario|last4=Rochau|first4=Boyke|last5=Stolte|first5=Andrea|last6=Andersen|first6=Morten|last7=Da Rio|first7=Nicola|last8=Henning|first8=Thomas|last9=Tognelli|first9=Emanuele|last10=Hogg|first10=David|last11=Clark|first11=Simon|last12=Waters|first12=Rens|year=2012|doi=10.1088/2041-8205/750/2/L44|arxiv = 1204.5481 |s2cid=5520745}}</ref>

This is one of the youngest clusters in the galaxy. The Arches Cluster is around 2.5 million years old, the Quintuplet cluster nearly double that, and the various open clusters containing red supergiants obviously even older.  Even R136 is thought to be near to 2 million years old. [[Trumpler 14]] in the [[Carina Nebula]] is thought to be as little as 300,000 - 500,000 years old, but is much less massive.<ref name=zwart/>

==References==
{{Reflist|refs=

<ref name=ucac>{{cite journal
 | display-authors=1
 | last1=Zacharias | first1=N.
 | last2=Urban | first2=S. E.
 | last3=Zacharias | first3=M. I.
 | last4=Wycoff | first4=G. L.
 | last5=Hall | first5=D. M.
 | last6=Germain | first6=M. E.
 | last7=Holdenried | first7=E. R.
 | last8=Winter | first8=L.
 | title=The Second U.S. Naval Observatory CCD Astrograph Catalog (UCAC2)
 | volume=1289 | journal=CDS/ADC Collection of Electronic Catalogues
 | year=2003 | bibcode=2003yCat.1289....0Z
 }}</ref>

<ref name=crowther>{{Cite journal
 | last1=Crowther | first1=P. A.
 | last2=Schnurr | first2=O.
 | last3=Hirschi | first3=R.
 | last4=Yusof | first4=N.
 | last5=Parker | first5=R. J.
 | last6=Goodwin | first6=S. P.
 | last7=Kassim | first7=H. A.
 | title=The R136 star cluster hosts several stars whose individual masses greatly exceed the accepted 150 M<sub>⊙</sub> stellar mass limit
 | journal=[[Monthly Notices of the Royal Astronomical Society]]
 | volume=408 | issue=2 | pages=731–751 | year=2010
 | arxiv=1007.3284
 | bibcode=2010MNRAS.408..731C
 | doi=10.1111/j.1365-2966.2010.17167.x
| doi-access=free
 | s2cid=53001712
 }}</ref>


}}

==Further reading==
*[https://web.archive.org/web/20150610203637/http://www.mpia.de/imprs-hd/theses/thesis_pang.pdf A comprehensive study of the young star cluster HD 97950 in NGC 3603]

{{Carina (constellation)}}

{{DEFAULTSORT:HD 97950}}
[[Category:Carina (constellation)]]
[[Category:Henry Draper Catalogue objects|097950]]
[[Category:NGC 3603]]
[[Category:Open clusters]]
[[Category:Hipparcos objects|054948]]
[[Category:Wolf–Rayet stars]]
[[Category:Durchmusterung objects]]
[[Category:O-type main-sequence stars]]
[[Category:O-type supergiants]]
[[Category:O-type giants]]
[[Category:B-type supergiants]]